Effects of Cd injection on osmoregulation and stress indicators in freshwater Nile tilapia

Evaluation of metal contamination effects in piranhas through biomonitoring and multi biomarkers approach

The present field study aimed to assess the water quality of the Itacaiúnas River, located at the eastern part of the Brazilian Amazon, using water's physicochemical parameters, ecological risk assessment in sediments, biomarkers and metal bioaccumulation in piranhas at two points: upstream (P1) and downstream (P2), and the type of season (Dry and Rainy). We revealed a significant difference between the points and the seasons. Concerning, the concentration of metals (Cd, Cu, Zn, Cr, and Hg) in sediment and water, we reported significant concentrations of Cd and Cu especially on P2 at dry season. The fish gills collected in P2 showed various types of damages (moderate and severe), furthermore, the Degree of Tissue Change (DTC) reported a significant difference between points, highlighting the dreadful condition in animals' health originated from this point. In terms of the biotransformation enzyme, the GST activity was higher in fishes from P2 in both seasons. The obtained results showed clear signs of stress in fish from the downstream point. Linear correlation analysis exhibited that the biomarkers' response could be linked to the detected metals bioaccumulation. This field investigation provides baseline data on pollution status in this region and the results showed that although the overall potential ecological risks of the metals were considered low at our sampling sites including cadmium, however, Cd posed a noteworthy monomial potential ecological risk factor. Strong evidence of correlation was obtained between Cd in the environment with the gills' damage in fishes from P2. The results also indicated that S. rhombeus could be useful for biomonitoring species for assessing metal contamination.

Short-term mercury exposure in tilapia (Oreochromis niloticus) at different salinities: impact on serum osmoregulation, hematological parameters, and Na+/K+-ATPase level

The objectives of this study were to analyze and compare the effects of mercury (Hg) exposure on osmoregulation and hematological responses in East Java strain tilapia (Oreochromis niloticus). Fish were exposed to 0, 0.1, and 1 mg L-1 Hg at 0, 5, 10, and 15 g L-1 salinities, and serum osmolality (SO), ion level, hematological parameters, and sodium (Na+)/potassium (K+)-ATPase (NKA) levels in the gills and kidney were assessed after 96 h of exposure. SO significantly increased in fish exposed to Hg at 15 g L-1 salinity compared with those exposed at 0, 5, 10, and 15 g L-1 salinities, but SO did not significantly increase in fish exposed to Hg at 5 and 10 g L-1 salinities compared with those exposed at 0 g L-1 salinity. At 15 g L-1 salinity, the Na+ level was significantly different from that at 0, 5, and 10 g L-1 salinities. The chloride ion level significantly increased only at 15 g L-1 salinity. Furthermore, the K+ level was significantly different at 10 and 15 g L-1 salinities from that at 0 and 5 g L-1 salinities. Hematocrit and hemoglobin levels and red blood cell and white blood cell (WBC) counts were not significantly different among all salinities. At 15 g L-1 salinity, the NKA level in the gills was significantly different from that at 0 g L-1 salinity, but in the kidney, there was no difference among all salinities. These data provide useful information for future reference and aquaculture practices to reduce Hg effects on tilapia. In conclusion, higher salinity reduced the effect of Hg on the K+ level and WBC count in tilapia.

Effects of Salinity on Survival and Growth of Gurami Sago (<I>Osphronemus goramy</I>, Lacepède, 1801) Juveniles

BACKGROUND AND OBJECTIVE

Gurami Sago Osphronemus goramy (O. goramy) are an herbivorous freshwater finfish species native in Indonesia. This species has not yet been cultured commercially in brackish water. A 60-days study was conducted to evaluate the effects of salinity on survival and growth of O. goramy.

MATERIALS AND METHODS

Two independent experiments were performed to determine the effects of salinity on survival and growth of juvenile O. goramy, first one was to determine the median lethal salinity (MLS-5096 h) and second one was to assess the survival and growth at different sub-lethal salinities. In MLS-5096 h study 0.0, 4.0, 8.0, 12.0 and 16.0 ppt salinities were used to initially find out the salinity tolerance range. Accordingly, a definitive salinity tolerance test was done in next phase to find out exact median lethal salinity by directly transferring the test species to 13.0, 14.0, 15.0 and 16.0 ppt salinity for 96 h. The median lethal salinity of O. goramy was estimated at 14.0 ppt. In the second experiment, survival and growth of the O. goramy were recorded at salinities 4.0, 8.0 and 12.0 ppt along with 0.0 ppt as control during 60 days.

RESULTS

Osigni goramy exhibited lowest final average weight at 12.0 ppt salinity and significantly highest at 4.0 ppt salinity. Highest SGR and weight gain were obtained at 4.0 ppt followed by 0 ppt, 8 ppt and 12 ppt salinity. All treatments were significantly (p<0.05). Survival rate of O. goramy varied between 76.45% (at 0.0 ppt) and 66.66% (at 12.0 ppt).

CONCLUSION

The O. goramy grew and survived satisfactorily at 0.0 to12.0 ppt salinities, implying that the species can be cultured commercially in brackish water, in view of in Indonesia, there are many abandoned shrimp ponds.